import com.fasterxml.jackson.databind.ObjectMapper;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 * @program: MessageMall
 * @author: JCM
 * @create: 2022-11-26 17:31
 * @description:
 **/
@WebServlet("/message")
public class MessageServlet extends HttpServlet {

    private ObjectMapper objectMapper = new ObjectMapper();

    // 负责页面获取数据
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 显式声明当前的响应数据格式
        resp.setContentType("application/json; charset=utf8");
        // 把 message 转成 json 字符串，并且返回给页面
        List<Message> messageList = null;

        try {
            messageList = load();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        resp.getWriter().write(objectMapper.writeValueAsString(messageList));
    }


    // 提交数据
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取到 body 中的数据 并解析
        Message message = objectMapper.readValue(req.getInputStream(),Message.class);
        // 把这个 message 保存一下，简单的办法就是保存在内存中

        try {
            save(message);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        resp.setStatus(200);
        System.out.println("提交数据成功：from=" + message.getFrom()
        + ", to="+ message.getTo()+", message="+ message.getMessage());

    }
    private List<Message> load() throws SQLException {
        // 从数据库中查询数据

        //1. 先有一个数据源
        DataSource dataSource = DBUtil.getDataSource();

        // 2. 建立连接
        Connection connection = dataSource.getConnection();

        //3. 构造 SQL
        String sql = "select * from message";
        PreparedStatement statement = connection.prepareStatement(sql);

        // 4. 执行SQL
        ResultSet resultSet = statement.executeQuery();

        // 5. 遍历结果集合
        List<Message> messageList = new ArrayList<>();
        while (resultSet.next()) {
            Message message = new Message();
            message.setFrom(resultSet.getString("from"));
            message.setTo(resultSet.getString("to"));
            message.setMessage(resultSet.getString("message"));
            messageList.add(message);
        }
        //6. 关闭连接
        statement.close();
        connection.close();
        return messageList;
    }

    private void save(Message message) throws SQLException {
        // 把数据保存在数据库中

        //1. 先有一个数据源
        DataSource dataSource = DBUtil.getDataSource();

        // 2. 建立连接
        Connection connection = dataSource.getConnection();

        // 3. 构造 SQL
        String sql = "insert into message value(?,?,?)";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setString(1,message.getFrom());
        statement.setString(2,message.getTo());
        statement.setString(3,message.getMessage());

        //4. 执行 SQL
        int ret = statement.executeUpdate();
        System.out.println("ret= "+ ret);

        //5.关闭连接
        statement.close();
        connection.close();
    }
}
